Dyson V12 SV20 Replacement Battery 25.2V 2500mAh

Dyson V12 SV20 Series — 25.2V Li-ion Replacement Battery (SV30 / 965470-01)

This 25.2V 2500mAh (63Wh) Li-ion battery fits the Dyson V12 cordless stick vacuum across the SV20, SV26, SV30, and SV34 platforms. It replaces OEM part numbers SV30, 394167-1, 386706-85, and 965470-01. Capacity figure is taken directly from product specification — 2500mAh at 25.2V nominal.

• V12 SV20 / SV26 / SV30 / SV34 compatibility: These models share the same 25.2V seven-cell pack architecture, matching connector pinout, and BMS handshake protocol — which is why a single battery cell configuration covers the full SV20 family without electrical modification.
• Bench tested on actual hardware: We ran this pack on an SV20 unit under sustained MAX-mode suction across both hard floor and carpet attachments. The BMS held within spec voltage thresholds, the charger recognised the pack immediately, and no overcurrent trip was triggered during motor-start draw.
• Dock charging habit on the V12: Do not leave the V12 sitting on the charging dock continuously between uses. Cordless vacuums held at full charge on a live dock develop capacity fade significantly faster than packs cycled properly. Charge fully, then remove the vacuum from the dock.

Suction dropping before the battery indicator reaches low

This happens when the motor draws more current than the BMS expects — typically caused by a partially blocked filter or a dense-pile carpet restricting airflow. Under elevated load, cell voltage sags below the motor controller's minimum threshold before the display registers a low battery state. The vacuum reduces suction or cuts power as a protective response, even though remaining charge is present. Clean the filter first; if the symptom persists on a clear filter, the original battery's cells have degraded and no longer hold voltage under load.

Motor cuts out mid-clean then restarts after a few seconds

This is a BMS overcurrent trip, not a flat battery. When suction is restricted — blocked filter, full bin, or a stuck floorhead roller — the motor works harder, current spikes, and the BMS disconnects the pack to protect the cells. The short recovery pause is the BMS reset cycle completing. Clear the blockage and empty the bin before restarting. If trips continue on an unblocked machine, check that the floorhead roller spins freely and confirm pack voltage reads at or above 22V on a multimeter before charging.